An electrical junction box provides a connection point for electrical wiring and/or conduits. Electrical conduits typically terminate at the sides of the junction box and cables and/or wires pass through the sidewalls to the interior. Inside the junction box, the cables and/or wires may be connected to other wires and/or pass through. The junction box may provide access, protection, and structural support for the electrical system.
The National Electric Code (NEC) is a North American standard for installation of electric conductors within or on buildings. The NEC defines Class 2 circuits with limited maximum voltage and current in comparison to mains electricity (or “line power”) delivered to buildings and used for general applications. The Class limits allow reduced requirements for wire size, derating factors, overcurrent protection, insulation, wiring methods, installation materials, etc. Using Class 2 circuits may reduce costs and improve flexibility.
In exchange for these benefits, the NEC requires Class 2 circuits must be used only for dry, indoor circuits, cannot be used in hazardous locations, must be grounded, and must be separated from other circuits. Compliance with these requirements may add components and/or complexity, especially if mains electricity is used in the same rooms or buildings. For example, the KNX standard widely used in Europe for network communications protocol for building automation does not separate line power from Class 2 circuits as required by the NEC, so multiple circuits may be required to implement such building automation solutions in North America.